To calculate the time period of these pre–jet oscillations, we apply a wavelet analysis technique. For the significance of time periods in the wavelet spectra, we take a significance test into
account and the levels higher than or equal to
95% are labeled as real. The significance test and the
wavelet analysis technique is well described by [1]}.
The cone of influence (COI) regions
make
an important background for the edge effect at the
start and end point of the time range ([2]}; [3]}).
